In recent years, display devices are becoming remarkably popular and, among them, liquid crystal display devices are widely used as a flat display panel.
Generally, the liquid crystal display device has a structure where a color filter forming substrate having a black matrix layer comprising a light-shielding colored layer and colored layers of respective colors disposed on one side of a transparent substrate, and a counter electrode substrate (also referred to as “TFT substrate”) are disposed opposite to each other with a prescribed space, wherein liquid crystal was encapsulated. A color image is displayed by controlling light transmittance of pixels of the colored layers of respective colors by electrically controlling orientation of the liquid crystal.
In such a liquid crystal display device, quality of the color filter forming substrate governs display quality itself.
On the other hand, recently, multifunctional terminals (also referred to as high-performance terminals) are spreading extensively and tablet-type multifunctional terminals are also expected to spread rapidly. While liquid crystal display devices are being used as a display of these terminals, high display quality and good design characteristics are required of the display devices.
For example, there is a case where a tablet-type multifunctional terminal is using a color filter forming substrate 110 for a display device comprising: as shown in FIG. 6A, a transparent substrate as a base material 111; and, on one side of the base material 111, colored layers 113 of respective colors for a color filter disposed in a region for display 113S and a light-shielding colored layer referred to as a frame portion 112 disposed as a region not for display around a periphery of the region for display 113S.
FIG. 6A is a plan view of a conventional color filter forming substrate; FIG. 6B and FIG. 6C are views taken in directions of arrows along E1-E2 and E3-E4, respectively, in FIG. 6A; FIG. 6D is an enlarged view of the E5 portion of FIG. 6A; and FIG. 6E is an enlarged view of the E6 portion of FIG. 6A.
FIG. 7 is a plan view of a tablet-type multifunctional terminal 120 which uses the color filter forming substrate 110 shown in FIGS. 6A to 6E.
And, usually, the colored layers of respective colors for the color filter, the colored layer for the black matrix, and the colored layer for the frame portion have been formed by photolithography processes. And the frame portion 112 and the black matrix (not shown in the figure) have been formed together by the same photolithography process.
The tablet-type multifunctional terminal 120 usually uses the color filter forming substrate 110 shown in FIGS. 6A to 6E, where the side of the base material 111 comprising a transparent substrate faces the side of a frame 121 and a part of the frame portion 112 corresponds to the non-display area 123. A display area 122 and the non-display area 123 of about 1 mm width are so designed that they are visible from a viewer's side through an opening inside the frame 121.
The main reasons why the width of the non-display area 123 is designed to be about 1 mm as just described are to make the whole display area surely visible from a viewer and to provide some latitude in positional accuracy between a display panel using the color filter forming substrate 110 and the frame.
However, in the tablet-type multifunctional terminal 120 shown in FIG. 7, when display on the display area 122 is turned off, a region of the frame portion, which is the non-display area 123 around the display area 122, looks brighter than the display area 122, resulting in a distinct difference between the display region 122 and the non-display area 123. This diminishes the visual quality and has been a problem.
Additionally, in the above, explanations were made mainly with reference to liquid crystal display devices as an example. However, the above-mentioned problem is not limited to the liquid crystal display devices but may occur similarly to any display device which uses a color filter forming substrate having a frame portion in a region not for display around a periphery of a region for display.